This invention relates to improvements in the surgical treatment of bone conditions of the human and other animal bone systems and, more particularly, to an inflatable balloon-like device for use in treating such bone conditions. Osteoporosis, avascular necrosis and bone cancer are diseases of bone that predispose the bone to fracture or collapse. There are 2 million fractures each year in the United States, of which about 1.3 million are caused by osteoporosis. Avascular necrosis and bone cancers are more rare but can cause bone problems that are currently poorly addressed.
In U.S. Pat. Nos. 4,969,888 and 5,108,404, an apparatus and method are disclosed for the fixation of fractures or other conditions of human and other animal bone systems, both osteoporotic and non-osteoporotic. The apparatus and method are especially suitable for use in the fixation of, but not limited to, vertebral body compression fractures, Colles fractures and fractures of the proximal humerus.
The method disclosed in these two patents includes a series of steps which a surgeon or health care provider can perform to form a cavity in pathological bone (including but not limited to osteoporotic bone, osteoporotic fractured metaphyseal and epiphyseal bone, osteoporotic vertebral bodies, fractured osteoporotic vertebral bodies, fractures of vertebral bodies due to tumors especially round cell tumors, avascular necrosis of the epiphyses of long bones, especially avascular necrosis of the proximal femur, distal femur and proximal humerus and defects arising from endocrine conditions).
The method further includes an incision in the skin (usually one incision, but a second small incision may also be required if a suction egress is used) followed by the placement of a guide pin which is passed through the soft tissue down to and into the bone.
The method further includes drilling the bone to be treated to form a cavity or passage in the bone, following which an inflatable balloon-like device is inserted into the cavity or passage and inflated. The inflation of the inflatable device causes a compacting of the cancellous bone and bone marrow against the inner surface of the cortical wall of the bone to further enlarge the cavity or passage. The inflatable device is then deflated and then is completely removed from the bone. A smaller inflatable device (a starter balloon) can be used initially, if needed, to initiate the compacting of the bone marrow and to commence the formation of the cavity or passage in the cancellous bone and marrow. After this has occurred, a larger, inflatable device is inserted into the cavity or passage to further compact the bone marrow in all directions.
A flowable biocompatible filling material, such as methylmethacrylate cement or a synthetic bone substitute, is then directed into the cavity or passage and allowed to set to a hardened condition to provide structural support for the bone. Following this latter step, the insertion instruments are removed from the body and the incision in the skin is covered with a bandage.
While the apparatus and method of the above patents provide an adequate protocol for the fixation of bone, it has been found that the compacting of the bone marrow and/or the trabecular bone and/or cancellous bone against the inner surface of the cortical wall of the bone to be treated can be significantly improved with the use of inflatable devices that incorporate additional engineering features not heretofore described and not properly controlled with prior inflatable devices in such patents. A need has therefore arisen for improvements in the shape, construction and size of inflatable devices for use with the foregoing apparatus and method, and the present invention satisfies such need.
A review of the prior art relating to the manufacture of balloons shows that a fair amount of background information has been amassed in the formation of guiding catheters which are introduced into cardiovascular systems of patients through the brachial or femoral arteries. However, there is a scarcity of disclosures relating to inflatable devices used in bone, and none for compacting bone marrow in vertebral bodies and long bones.
In a dilatation catheter, the catheter is advanced into a patient until a balloon is properly positioned across a lesion to be treated. The balloon is inflated with a radiopaque liquid at pressures above four atmospheres to compress the plaque of the lesion to thereby dilate the lumen of the artery. The balloon can then be deflated, then removed from the artery so that the blood flow can be restored through the dilated artery.
A discussion of such catheter usage technique is found and clearly disclosed in U.S. Pat. No. 5,163,989. Other details of angioplasty catheter procedures, and details of balloons used in such procedures can be found in U.S. Pat. Nos. 4,323,071, 4,332,254, 4,439,185, 4,168,224, 4,516,672, 4,538,622, 4,554,929, and 4,616,652.
Extrusions have also been made to form prism shaped balloons using molds which require very accurate machining of the interior surface thereof to form acceptable balloons for angioplastic catheters. However, this technique of extrusion forms parting lines in the balloon product which parting lines are limiting in the sense of providing a weak wall for the balloon itself.
U.S. Pat. No. 5,163,989 discloses a mold and technique for molding dilatation catheters in which the balloon of the catheter is free of parting lines. The technique involves inflating a plastic member of tubular shape so as to press it against the inner molding surface which is heated. Inflatable devices are molded into the desired size and shape, then cooled and deflated to remove it from the mold. The patent states that, while the balloon of the present invention is especially suitable for forming prism-like balloons, it can also be used for forming balloons of a wide variety of sizes and shapes.
A particular improvement in the catheter art with respect to this patent, namely U.S. Pat. No. 4,706,670, is the use of a coaxial catheter with inner and outer tubing formed and reinforced by continuous helical filaments. Such filaments cross each other causing the shaft of the balloon to become shorter in length while the moving portion of the shank becomes longer in length. By suitably balancing the lengths and the angle of the weave of the balloon and moving portions of the filaments, changes in length can be made to offset each other. Thus, the position of the inner and outer tubing can be adjusted as needed to keep the balloon in a desired position in the blood vessel.
Other disclosures relating to the insertion of inflatable devices for treating the skeleton of patients include the following;
U.S. Pat. No. 4,313,434 relates to the fixation of a long bone by inserting a deflated flexible bladder into a medullary cavity, inflating the balloon bladder, sealing the interior of the long bone until healing has occurred, then removing the bladder and filling the opening through which the bladder emerges from the long bone.
U.S. Pat. No. 5,102,413 discloses the way in which an inflatable bladder is used to anchor a metal rod for the fixation of a fractured long bone.
Other references which disclose the use of balloons and cement for anchoring of a prosthesis include U.S. Pat. Nos. 5,147,366, 4,892,550, 4,697,584, 4,562,598, and 4,399,814.
A Dutch patent, NL 901858, discloses a means for fracture repair with a cement-impregnated bag which is inflated into a preformed cavity and allowed to harden.
It can be concluded from the foregoing review of the prior art that there is little or no substantive information on inflatable devices used to create cavities in bone. It does not teach the shape of the balloon which creates a cavity that best supports the bone when appropriately filled. It does not teach how to prevent balloons from being spherical when inflated, when this is desired. Current medical balloons can compress bone but are too small and generally have the wrong configuration and are generally not strong enough to accomplish adequate cavity formation in either the vertebral bodies or long bones of the body.
U.S. Pat. Nos. 4,969,888 and 5,108,404 disclose a checker-shaped balloon for compressing cancellous bone, but does not provide information on how this balloon remains in its shape when inflated.
Thus, the need continues for an improved inflatable device for use with pathological bones and the treatment thereof.
The present invention is directed to a balloon-like inflatable device or balloon for use in carrying out the apparatus and method of the above-mentioned patents U.S. Pat. Nos. 4,969,888 and 5,108,404. Such inflatable devices, hereinafter sometimes referred to as balloons, have shapes for compressing cancellous bone and marrow (also known as medullary bone or trabecular bone) against the inner cortex of bones whether the bones are fractured or not.
In particular, the present invention is directed to a balloon for use in treating a bone predisposed to fracture or to collapse. The balloon comprises an inflatable, non-expandable balloon body for insertion into said bone. The body has a predetermined shape and size when substantially inflated sufficient to compress at least a portion of the inner cancellous bone to create a cavity in the cancellous bone and to restore the original position of the outer cortical bone, if fractured or collapsed. The balloon body is restrained to create said predetermined shape and size so that the fully inflated balloon body is prevented from applying substantial pressure to the inner surface of the outer cortical bone if said bone is unfractured or uncollapsed.
In addition to the shape of the inflatable device itself, another aspect of importance is the construction of the wall or walls of the balloon such that proper inflation the balloon body is achieved to provide for optimum compression of all the bone marrow. The material of the balloon is also desirably chosen so as to be able to fold the balloon so that it can be inserted quickly and easily into a bone using a guide pin and a cannula, yet can also withstand high pressures when inflated. The balloon can also include optional ridges or indentations which are left in the cavity after the balloon has been removed, to enhance the stability of the filler. Also, the inflatable device can be made to have an optional, built-in suction catheter. This is used to remove any fat or fluid extruded from the bone during balloon inflation in the bone. Also, the balloon body can be protected from puncture by the cortical bone or canula by being covered while inside the canula with an optional protective sleeve of suitable material, such as Kevlar or PET or other polymer or substance that can protect the balloon. The main purpose of the inflatable device, therefore, is the forming or enlarging of a cavity or passage in a bone, especially in, but not limited to, vertebral bodies.
The primary object of the present invention is to provide an improved balloon-like inflatable device for use in carrying out a surgical protocol of cavity formation in bones to enhance the efficiency of the protocol, to minimize the time prior to performing the surgery for which the protocol is designed and to improve the clinical outcome. These balloons approximate the inner shape of the bone they are inside of in order to maximally compress cancellous bone. They have additional design elements to achieve specific clinical goals. Preferably, they are made of inelastic material and kept in their defined configurations when inflated, by various restraints, including (but not limited to) use of inelastic materials in the balloon body, seams in the balloon body created by bonding or fusing separate pieces of material together, or by fusing or bonding together opposing sides of the balloon body, woven material bonded inside or outside the balloon body, strings or bands placed at selected points in the balloon body, and stacking balloons of similar or different sizes or shapes on top of each other by gluing or by heat fusing them together. Optional ridges or indentations created by the foregoing structures, or added on by bonding additional material, increases stability of the filler. Optional suction devices, preferably placed so that if at least one hole is in the lowest point of the cavity being formed, will allow the cavity to be cleaned before filling.
Among the various embodiments of the present invention are the following:
1. A doughnut (or torus) shaped balloon with an optional built-in suction catheter to remove fat and other products extruded during balloon expansion.
2. A balloon with a spherical outer shape surrounded by a ring-shaped balloon segment for body cavity formation.
3. A balloon which is kidney bean shaped in configuration. Such a balloon can be constructed in a single layer, or several layers stacked on top of each other.
4. A spherically shaped balloon approximating the size of the head of the femur (i.e. the proximal femoral epiphysis). Such a balloon can also be a hemisphere.
5. A balloon in the shape of a humpbacked banana or a modified pyramid shape approximating the configuration of the distal end of the radius (i.e. the distal radial epiphysis and metaphysis).
6. A balloon in the shape of a cylindrical ellipse to approximate the configuration of either the medial half or the lateral half of the proximal tibial epiphysis. Such a balloon can also be constructed to approximate the configuration of both halves of the proximal tibial epiphysis.
7. A balloon in the shape of sphere on a base to approximate the shape of the proximal humeral epiphysis and metaphysis with a plug to compress cancellous bone into the diaphysis, sealing it off.
8. A balloon device with optional suction device.
9. Protective sheaths to act as puncture guard members optionally covering each balloon inside its catheter.
The present invention, therefore, provides improved, inflatable devices for creating or enlarging a cavity or passage in a bone wherein the devices are inserted into the bone. The configuration of each device is defined by the surrounding cortical bone and adjacent internal structures, and is designed to occupy about 70-90% of the volume of the inside of the bone, although balloons that are as small as about 40% and as large as about 99% are workable for fractures. In certain cases, usually avascular necrosis, the balloon size may be as small as 10% of the cancellous bone volume of the area of bone being treated, due to the localized nature of the fracture or collapse. The fully expanded size and shape of the balloon is limited by additional material in selected portions of the balloon body whose extra thickness creates a restraint as well as by either internal or external restraints formed in the device including, but not limited to, mesh work, a winding or spooling of material laminated to portions of the balloon body, continuous or non-continuous strings across the inside held in place at specific locations by glue inside or by threading them through to the outside and seams in the balloon body created by bonding two pieces of body together or by bonding opposing sides of a body through glue or heat. Spherical portions of balloons may be restrained by using inelastic materials in the construction of the balloon body, or may be additionally restrained as just described. The material of the balloon is preferably a non-elastic material, such as polyethylene tetraphthalate (PET), Kevlar or other patented medical balloon materials. It can also be made of semi-elastic materials, such as silicone or elastic material such as latex, if appropriate restraints are incorporated. The restraints can be made of a flexible, inelastic high tensile strength material including, but not limited, to those described in U.S. Pat. No. 4,706,670. The thickness of the balloon wall is typically in the range of {fraction (2/1000)} ths to {fraction (25/1000)} ths of an inch, or other thicknesses that can withstand pressures of up to 250-400 psi.
A primary goal of percutaneous vertebral body augmentation of the present invention is to provide a balloon which can create a cavity inside the vertebral body whose configuration is optimal for supporting the bone. Another important goal is to move the top of the vertebral body back into place to retain height where possible, however, both of these objectives must be achieved without fracturing the cortical wall of the vertebral body. This feature could push vertebral bone toward the spinal cord, a condition which is not to be desired.
The present invention satisfies these goals through the design of inflatable devices to be described. Inflating such a device compresses the calcium-containing soft cancellous bone into a thin shell that lines the inside of the hard cortical bone creating a large cavity.
At the same time, the biological components (red blood cells, bone progenitor cells) within the soft bone are pressed out and removed by rinsing during the procedure. The body recreates the shape of the inside of an unfractured vertebral body, but optimally stops at approximately 70 to 90% of the inner volume. The balloons of the present invention are inelastic, so maximally inflating them can only recreate the predetermined shape and size. However, conventional balloons become spherical when inflated. Spherical shapes will not allow the hardened bone cement to support the spine adequately, because they make single points of contact on each vertebral body surface (the equivalent of a circle inside a square, or a sphere inside a cylinder). The balloons of the present invention recreate the flat surfaces of the vertebral body by including restraints that keep the balloon in the desired shape. This maximizes the contacts between the vertebral body surfaces and the bone cement, which strengthens the spine. In addition, the volume of bone cement that fills these cavities creates a thick mantle of cement (4 mm or greater), which is required for appropriate compressive strength. Another useful feature, although not required, are ridges in the balloons which leave their imprint in the lining of compressed cancellous bone. The resulting bone cement xe2x80x9cfingersxe2x80x9d provide enhanced stability.
The balloons which optimally compress cancellous bone in vertebral bodies are the balloons listed as balloon types 1, 2 and 3 above. These balloons are configured to approximate the shape of the vertebral body. Since the balloon is chosen to occupy 70 to 90% of the inner volume, it will not exert undue pressure on the sides of the vertebral body, thus the vertebral body will not expand beyond its normal size (fractured or unfractured). However, since the balloon has the height of an unfractured vertebral body, it can move the top, which has collapsed, back to its original position.
A primary goal of percutaneous proximal humeral augmentation is to create a cavity inside the proximal humerus whose configuration is optimal for supporting the proximal humerus. Another important goal is to help realign the humeral head with the shaft of the humerus when they are separated by a fracture. Both of these goals must be achieved by exerting pressure primarily on the cancellous bone, and not the cortical bone. Undue pressure against the cortical bone could conceivably cause a worsening of a shoulder fracture by causing cortical bone fractures.
The present invention satisfies these goals through the design of the inflatable devices to be described. Inflating such a device compresses the cancellous bone against the cortical walls of the epiphysis and metaphysis of the proximal humerus thereby creating a cavity. In some cases, depending on the fracture location, the balloon or inflatable device may be used to extend the cavity into the proximal part of the humeral diaphysis.
Due to the design of the xe2x80x9csphere on a standxe2x80x9d balloon (described as number 7 above), the cavity made by this balloon recreates or approximates the shape of the inside cortical wall of the proximal humerus. The approximate volume of the cavity made by the xe2x80x9cspherical on a stand balloonxe2x80x9d is 70 to 90% that of the proximal humeral epiphysis and metaphysis, primarily, but not necessarily exclusive of, part of the diaphysis. The shape approximates the shape of the humeral head. The xe2x80x9cbasexe2x80x9d is designed to compress the trabecular bone into a xe2x80x9cplugxe2x80x9d of bone in the distal metaphysis or proximal diaphysis. This plug of bone will prevent the flow of injectable material into the shaft of the humerus, improving the clinical outcome. The sphere can also be used without a base.
A primary goal of percutaneous distal radius augmentation is to create a cavity inside the distal radius whose configuration is optimal for supporting the distal radius. Another important goal is to help fine tune fracture realignment after the fracture has been partially realigned by finger traps. Both of these goals must be achieved by exerting pressure primarily on the cancellous bone and not on the cortical bone. Excessive pressure against the cortical bone could conceivably cause cortical bone fractures, thus worsening the condition.
The present invention satisfies these goals through the design of inflatable devices either already described or to be described.
The design of the xe2x80x9chumpbacked bananaxe2x80x9d, or modified pyramid design (as described as number 5 above), approximates the shape of the distal radius and therefore, the cavity made by this balloon approximates the shape of the distal radius as well. The approximate volume of the cavity to be made by this humpbacked banana shaped balloon is 70 to 90% that of the distal radial epiphysis and metaphysis primarily of, but not necessarily exclusive of, some part of the distal radial diaphysis. Inflating such a device compresses the cancellous bone against the cortical walls of the epiphysis and metaphysis of the distal radius in order to create a cavity. In some cases, depending on the fracture location, the osseous balloon or inflatable device may be used to extend the cavity into the distal part of the radial diaphysis.
A primary goal of percutaneous femoral head (or humeral head) augmentation is to create a cavity inside the femoral head (or humeral head) whose configuration is optimal for supporting the femoral head. Another important goal is to help compress avascular (or aseptic) necrotic bone or support avascular necrotic bone is the femoral head. This goal may include the realignment of avascular bone back into the position it previously occupied in the femoral head in order to improve the spherical shape of the femoral head. These goals must be achieved by exerting pressure primarily on the cancellous bone inside the femoral head.
The present invention satisfied these goals through the design of inflatable devices either already described or to be described.
The design of the spherical osseous balloon (described as balloon type 4 above) approximates the shape of the femoral head and therefore creates a cavity which approximates the shape of the femoral head as well. (It should be noted that the spherical shape of this inflatable device also approximates the shape of the humeral head and would, in fact, be appropriate for cavity formation in this osseous location as well.) Inflating such a device compresses the cancellous bone of the femoral head against its inner cortical walls in order to create a cavity. In some cases, depending upon the extent of the avascular necrosis, a smaller or larger cavity inside the femoral head will be formed. In some cases, if the area of avascular necrosis is small, a small balloon will be utilized which might create a cavity only 10 to 15% of the total volume of the femoral head. If larger areas of the femoral head are involved with the avascular necrosis, then a larger balloon would be utilized which might create a much larger cavity, approaching 80 to 90% of the volume of the femoral head.
The hemispherical balloon approximates the shape of the top half of the femoral (and humeral) head, and provides a means for compacting cancellous bone in an area of avascular necrosis or small fracture without disturbing the rest of the head. This makes it easier to do a future total joint replacement if required.
A primary goal of percutaneous proximal tibial augmentation is to create a cavity inside the proximal tibia whose configuration is optimal for supporting either the medial or lateral tibial plateaus. Another important goal is to help realign the fracture fragments of tibial plateau fractures, particularly those features with fragments depressed below (or inferior to) their usual location. Both of these objectives must be achieved by exerting pressure on primarily the cancellous bone and not the cortical bone. Pressure on the cortical bone could conceivably cause worsening of the tibial plateau fracture.
The present invention satisfies these goals through the design of the inflatable devices to be described. Inflating such a device compresses the cancellous bone against the cortical walls of the medial or lateral tibial plateau in order to create a cavity.
Due to the design of the xe2x80x9celliptical cylinderxe2x80x9d balloon (described as balloon type 6 above) the cavity made by this balloon recreates or approximates the shape of the cortical walls of either the medial or lateral tibial plateaus. The approximate volume of the cavity to be made by the appropriate elliptical cylindrical balloon is 50 to 90% of the proximal epiphyseal bone of either the medial half or the lateral half of the tibial.
Other objects of the present invention will become apparent as the following specification progresses reference being had to the accompanying drawings for an illustration of the invention.